Oil-contaminated water represents a significant hazardous waste problem in the industry. Oil-contaminated water is typically, but not exclusively, derived from air compressor condensants and transmission fluids; and such oil-contaminated water includes particulate material, emulsified, dissolved and free oils and metal ions which represent hazardous waste. These contaminants must be removed before the clean water may be discharged into the environment. The level of contamination permitted by government regulation varies; but typically, clean water should have less than twenty-five parts per million of oil and preferably, ten to five parts per million or lower. Metal contaminated water contains mainly petroleum, mineral, and hydrocarbon oils from a variety of industrial sources as well as chemical-type additives, such as: polyalfaolefins, diesters, glycols, polyglycols and the like, which also need to be removed prior to discharge of clean water.
Oil-water separating systems are the preferred and least costly method of treating oil-contaminated water and provide for a clean water discharge of less than twenty parts per million. Oil-water separation may be accomplished on-site; for example, by gravity carbon absorption technology, which is not wholly effective, or ultrafiltration technology, which is more effective in removing diesters, polyglycols, ETF and PAO contaminants.
One prior art commercially sold oil-water separator system which is quite effective in providing an on-site, oil-water separating system with clean water discharge, usually below twenty parts per million, comprises a system applying a combination of filters and hollow fiber membranes.
One oil-water separating system, a nanofiltration, separating, coalescing system, comprises a Balston.RTM. oil-water separator as described in Whatman Inc.'s, "Balston.RTM. Oil Water Separators"; Bulletin PK-56A, hereby incorporated by reference.
This nanofiltration system picks up free oil by a skimmer and removes continuously, the free oil from a process tank. The compressor condensate, the oil-water contaminate, is pumped into a prefiltered process tank and flows through a nanofiltration membrane module, which permits the permeation of only the water molecules to penetrate the membrane. The permeate water, virtually free of oil, is then discharged; while the unprocessed oil and water continues to flow though the hollow fiber membrane modules into a coalescing filter which transforms the emulsified and soluble oils into larger, free droplets of oils, which are then deposited into the processing tank. These larger oil droplets are then picked up by the oil skimmer which discharges the concentrated oil product from the processing tank for disposal.
While the automated, nanofiltration membrane, oil-water system is quite effective in removing a variety of contaminates, as well as particulates from contaminated oil-water, the employment of thin membrane modules are susceptible, from time to time, to oil plugging of the membrane surface; and further, the sheet or hollow fiber membrane is often very fragile, as well as being subject to oil flow blockage.
It is therefore desirable to provide for a new and improved oil-water separator automated system to provide for the continuous discharge of clean water from oil-contaminated water.